1. Field of the Invention
The invention relates to a rotor of a turbogenerator having direct gas cooling of the excitation winding, the excitation winding conductors being arranged in longitudinal slots in the rotor body of the rotor and these slots being closed by means of slot wedges, and an insulating strip being provided between the slot base and the excitation winding conductor located above it.
A rotor of this generic type is disclosed, for example, in US-A-4,152,610.
2. Discussion of Background
Different methods for direct cooling of the excitation winding have been developed in the course of time:
a) The cooling gas enters below the winding overhang of the rotor winding and is split in two directions at the start of the rotor body. One part of the cooling gas flows through the winding overhang conductors and leaves the winding overhang area through special openings which are arranged in the pole zone on the rotor body. However, the main part of the airflow enters the excitation winding, which is constructed from hollow conductors, on the body circumference and flows out in the body center (US-A-4,634,910). PA1 b) The cooling gas is passed to the conductors, underneath the excitation winding, along a special channel (keyway or subslot) in the slot. It emerges, seen in the axial direction, at various points (US-A-3,119,033 or US-A-4,152,610). PA1 c) A combination of methods a) and b). In this case, the gas supply for the excitation conductor section is effected in the rotor center by means of keyways or subslots, while the sections at the ends are supplied directly from the winding overhang area.
In all known variants, it is essential for the excitation winding conductors to be securely fixed in the rotor slots, which is normally done by means of slot wedges. In operation, the excitation conductors are pressed against the slot wedges by the centrifugal force effect and are thus also largely secured axially. However, seating phenomena in the event of centrifugal action and in operation lead to loosening in the conductor assembly. This can lead to relative movements occurring between the excitation conductors and the slot or wedge after interruptions in operation, for example in the event of shaft reversal or restarting of the machine. For this reason, resiliently elastic intermediate layers are installed in a prestressed manner between the slot wedge and winding. In the case of rotors without a keyway, resiliently elastic intermediate layers, generally so-called corrugated springs, are also used in the slot base. These intermediate layers must be fixed at at least one point, generally at the rotor body end, in the slot longitudinal direction. While the axial fixing of the resiliently elastic intermediate layers under the slot wedge does not present any problems, the design of the fixing of the intermediate layers on the slot base is more difficult in the case of rotors having a keyway and the corresponding elements must not constrict the cross section of the keyway. Manufacturing reasons and/or strength reasons prohibit the introduction of holes or the like into the slot.